Method and apparatus for bending plate and the like



April 29, 1947. MlLLARD ET AL 2,419,724

METHOD AND APPARATUS FOR BENDING PLATE AND THE LIKE Filed April 3, 19434 Sheets-Sheet l MM w Sm: m R L mm M v v mm m m Hm MW m E 5 April 29,1947. I E. H. MILLARD ET AL 2,419,724

METHJD AND APPARATUS FOR BENDING PLATE AND THE LIKE Filed April 3, 19434 Sheets-Sheet 2 INVENTORS EMMoR hf MIL MR0 and FEEDER/CK R. W/LSO/V,

April 29, 1947. E. H. MlLLARD T AL METHOD AND APPARATUS FOR BENDINGPLATE AND THE LIKE- Filed April 3, 1943 4 Sheets$heet 3 fig? ll a.

l1 Fig.5. 10

J0 INVENTORS f/hMae/iM/L MR0 and FEEDER/CK A. W/Lso/v,

April 29, 1947.

E. H. MILLARD ET AL 2,419,724

METHOD AND APPARATUS FOR BENDING PLATE AND THE LIKE Filed April 3, 19454 Sheets-Sheet 4 Patented Apr. 29, 1947 METHOD AND APPARATUS FOR BENDINGPLATE AND THE LIKE Emmor H. Millard, Mount Lebanon, and Frederick R.Wilson, Canonsburg, Pa., assignors to Steel Processing Company,Pittsburgh, Pa., a corporation of Pennsylvania Application April 3,1943, Serial No. 481,692

22 Claims. 1

This invention relates to a method of and apparatus for the bending ofplates, strips, bars and the like, and more especially to a method ofand apparatus for forming relatively heavy gauge flat plates ofconsiderable length into an elongated structure including a trough-likebody portion and lateral side flange portions, the cross-section ofwhich is approximately U-shape with flanges. Such a plate constructiondescribes the well known Isherwood plate, such plates being especiallyadaptable for use and extensively employed in ship constructions.

Our invention will be particularly described in connection with themethod and apparatus for the fabrication of such plates, but ourinvention is not to be limited to such manufacture, as it is alsoapplicable to the art of bending fiat plates into various angularconfigurations by the provision of bending means having spaced apartplate supports and bending elements and having a cooperating abutmentdisaligned with said supports to engage the upper surface of the plate,operable to effect bending of plates along predetermined lines while theplate is unclamped on said supports and movable into engagement with theabutment which may vary in cross-section.

As heretofore fabricated Isherwood plates have been formed by followinga plurality of independent bending operations producing too sharp bends,and have frequently been rejected due to the weakness developed at thebending lines of the predetermined shaped plate, and, when notdiscovered prior to assemblage, have caused serious trouble in use.

An object of our invention is to provide a new and improved simple andefiicient method of bending, whereby to eliminate the several steps ofbending heretofore followed and to produce a plate of the characterspecified having rounded bending lines or zones, free of the weaknessesheretofore present in such plates.

Further objects are; to bend the plates without the employment of thefrequently used male and female-die construction, or the like, wherebyto effect the desired bending without subjecting th work or plates toharmful pressure along the bending lines or zones to stretch or rupturethe fibers of the metal, as frequently hap ns; to provide new andimproved bending means for efiecting uniform bends, and a constructionof a character permitting a free travel of the material between theopposed upper and lower bending means employed.

In the accompanying drawings, which illustrate a preferred embodiment ofapparatus employed in the practice of our invention,

Fig. l is an enlarged transverse sectional view taken on line I-I ofFig. 2;

Fig. 2, a central longitudinal vertical sectional View;

Fig. 3, a horizontal sectional view taken on line III-III of Fig. 2;

Figs. 4-7 are diagrammatic views somewhat similar to Fig. 1, showing thesuccessive stages of bending the work or plate from the initial bendingto completion of the final form, as shown by Fig.

Fig. 8, a perspective view of the finished plate;

Fig. 9, a diagrammatic view particularly showing a power mechanism;

Fig. 10, an enlarged sectional view of a control valve; and

Fig. 11, a cross section on line X-X of Fig. 10;

Referring to the drawings, our invention comprises a skeleton frametunnel-like structure designated generally by 5, made up of structuralmembers including a base portion 6, side portions 1, the latterpreferably including vertical extend ing I-beams, and a top portion -8including cross members 9 suitably connected with and supported by themembers entering into the formation of the sides. The frame structurehowever, may be constructed in any suitable manner provided it isdesigned to house bending means'of a character embodying our inventionand particularly adapted for bending plates, strips and the like, ofconsiderable length and of relatively heavy gauge mate-'- rial.

The bending means or elements as illustrated include a series ofindependent bending units l0 disposed in alinement and extendinglongitudinally of and within the housing or framing, thus providingbending means for long sections of plate, etc. In lieu of the separateunits l0 they may be joined together to form a unitary elongated unit.Each of the several units comprises a stationary and a movable member orplaten, the upper platen II is secured to and supported by the crossmembers 9. This platen constitutes a stationary member against which thework is carried in the bending operation, the said member or platen I Ihaving mounted thereon suitable forming blocks or abutments forengagement with the work. As illustrated, the forming blocks orabutments on platen ll consist of centrally disposed depending members[2, suspended from the cross members and platen on hanger bolts I3. Thismember l2, a shown, includes a cap Piece l4 and intermediate removablefiller members orshims l5. Said cap piece M has parallel roundedwork-contacting edges a and its under surface 14* is preferably concave.Arranged on each side of the center member I2 are spaced apart elongatedWork contact members I6 having inclined diverging under surfaces l6adapted to bend metal plates through contact therewith at outer edges I6the shape of these surfaces affording an opportunity for the edgeportions of the plate to bend slightly beyond the horizontal plane to 3allow for spring-back of the metal into the horizontal plane.

The lower movable member H is mounted for vertical movement onstructural members 18 carried on the plunger 19 of a hydraulic cylinder20.

Suitable guide means consisting of guide rods 2| secured to the sideframing, engage grooves b disposed on the platen in alinement with thework contacting members [3 of the upper platen and extend throughoutthelength of the apparatus. This member I7 is further provided with acenter block or piece 23 disposed in alinement with the centraldepending member [2 of theupper platen, both members 12 and 23 extendingthe full length of the apparatus. Block or member 23 is raised centrallyto provide a work-contacting line or edge 23 The pedestals 22 may beprovided with wear-shoes 24 having rounded edges 24*, and the shoes maybe raised or lowered slightly by the employment of shims 25, tocompensate for wear. It will be noted that the upper surfaces of shoes24 are parallel to the surfaces Hi. This arrangement or the equivalentprovides line contact only of said shoes with the plate and such contactis disaligned with that at the edges lfi Our invention contemplateseither a simultaneous operation of all of the units it or an independentoperation of one or more units, depending upon the length of plate to bebent into the desired and predetermined configuration. The length of theplates most usually fabricated vary from twelve to forty-two feet andusually of a finished width of five feet. It will also be understoodthat our invention contemplates the production of plates having aconsiderable variation in depth as well as in the gauge of materialemployed and that owing to adjustability and arrangement of the bendingmeans embodied in our invention, all of the said variations may beprovided for with comparative case.

In the practice of our invention the plate or other member to be formedinto the predetermined configuration'and size, and indicated by theletter p in Figs. 1 and 2, is fed into the apparatus lengthwise from anend thereof and is supported and carried unclamp'ed upon the spacedapart elongated longitudinally extending work supporting elements orpedestals 22, mounted on the several vertically movable members orplatens ll. As illustrated and as preferred, in forming Isherwoodplates, for example, the plate is positioned on said members 22 in amanner to provide an unsupported central portion between the elements,which portion when brought into contact with the various alinedabutments or members l2 of the stationary members on platens II, by theupward movement of members ll, actuated by the hydraulic cylinders 20 orother suitable power means, forms the elongated work into a continuousmember having a cross-section including a trough or U-like portion dhaving inclined walls e, and edge flanges f.

The various stages of bending, are particularly shown by Figs. 4 to 7inclusive. It will be understood that the work is not clamped, butsimply rests above the supports and as the lower platens rise, theunsupported portion of the work between the pedestals orsupportingelements is carried into engagement with the rounded corners of thedepending centrally disposed abutments of the upper platens and on itsinitial bending engagement therewith the plate is caused to assume agenerally somewhat U-shape having a slightly dished center or roundedapex, the legs of the U extending or diverging upwardly at an angledefined by a line drawn from a corner of the center abutment to a pointshort of contact with the outside edge of fixed members it, as clearlyshown in Fig. 4. Attention is particularly called to the fact that theplate is bent through fulcruming and slidingon edges of the supportelements in cooperation with the fixed abutments.

When the plate has been bent as in Fig. 4, a continued movement of thelower platen or platens will cause the edges of the plate or work tocontact with the fixed members 16 as shown by Fig. 5, and thus start thebending to form the flanges, this bend being in anopposite or reverseangle to that of the inclined Walls of the trough portion or body. Acontinuation of the upward movement, as illustrated by Figs. 6 and '7,will complete the formation of the flange portions and during theformation of the flanges, the blocks 23 are carried sufliciently closeto the under faces of the aligned abutments of members [2 to flatten thecentral portion of the trough into a plane parallel with the plane ofthe flanges as clearly shown by Fig. 7.

Our invention contemplates an apparatus having a combination andarrangement of operative parts operable in such a manner that the workis not subjected to compressing, compacting, or clamping contact betweenopposing bending elements, but is only contacted by the apparatus at thelines, zones or fulcrum of bend up to final stage.

Thus, in our illustrative embodiment the upper and lower bendingelements do not make compressive contact with the plate or work, orcompress the material between the flxed and movable members to the endthat the metal is not tightly caught therebetween, and, consequently isfree to adjust itself and slide or travel between the opposed bendingmembers with the movement of r' the fibers at all times parallel,therefore resulting in no separation or weakening of the fibers.

Our invention is therefore to be distinguished from a method offabricating in which the metal of the work is clamped between opposingdies, for, in the latter case, compression of the fiber 0n the inside ofthe bend is caused, whereas the fibers on the outside in tension arestretched, this causes a definite line of cleavage in the grain of themetal between the portion in compression and the portion in tension,with a weakening at the bends.

It is apparent that at all times bending is efiected solely through edgeor line contact with the plate as all edges a, 23, 24 and I6 areparallel and sufficiently smooth or rounded. Said block 23 is centrallyraised as shown at 23 particularly to start and carry to completion thelast stage of metal flow as shown in Figs. 4 to 7. Cap M of black [2 ispreferably concave and block 23 is shaped as pointed out so that minimumpressure is required to produce a flat surface as there is only linecontact 50 that metal moves easily. The edge 21*! causes the metal tomove right and left around edges (1 without changing the granular orfiber structure in any way, all stresses and strains beingparallelduring this operation to avoid mashing or killing of the steel throughtrappi ng :.of 'the fibers at final bending points with resultingchanges in granular structure of metal at these points which would inmany instances cause fractures of the metal. The blocks l6 and 24 atedges H5 and 2& enable movement of the metal over rounded corners oredges as the metal movement at this stage comes from the center of block23, and at the same time the bending is progressing and when metalmovement has been completed, the bending has also been completed, and inthe process the mill rolling strains have worked out of the edges of theplate, and there is no wavy edge condition on the plate and the flangesof the plate are perfectly flat and in a plane approximately parallelwith the bottom of the formed plate. The speed of operation is such, incombination with the minimum number of lines of contact and roundedcorners, sufficiently lubricated, allows time for the metal to movefreely. The metal movement is reversed in the latter third of the upwardstroke of the platen ID as will be noted from considering Figs. 5, 6 and7.

Any suitable power mechanism may be employed for operating the apparatusprovided the mechanism includes means for controlling the length of thestroke of the hydraulic cylinders with distance between the workcontacting surfaces of the bending elements on the upper and lowerplatens whereby the opposing bending elements are never brought intobinding contact.

As particularly illustrated by Fig. 9, we employ an associated powermechanism including a pressure fluid system or line extending to theseveral cylinders 29 from a pump P, and an electrical control circuit.

A designates a fluid control valve in communication with a valvecontrolled main fluid pressure line or pipe g having a valve h. idesignate valve controlled branch lines leading to the respectivehydraulic cylinders and :i an exhaust line from the valve A to a fluidstorage tank k. The enlarged view of valve A (Fig. 10) shows thehydraulic line from pump to cylinders as being closed to pressure andopen for return of fluid to the supply tank, and in the diagrammaticView, Fig. 9, the plungers of the cylinders are shown in loweredposition.

To start the bending operation the valve A is opened to pressure fromthe pump by pressing a push button B of the electric circuit whichcloses a circuit through a solenoid c which pulls the valve down to openthe line and which closes the exhaust 7'.

Attached to any movable part of the apparatus, actuated by movement ofthe rising plunger, is an arm or switch closing device F. This arm isadjustably mounted, so that it may be adjusted with respect to itsdistance between its mounting and the switch arm of a switch S. When thepiston has moved to bring the arm into contact with the switch arm, acircuit is closed through solenoid E which moves the valve to close thefluid pressure line from the pump and put the line in exhaust.

We claim:

1. In apparatus for forming flat plate into substantially trough-likeform having side wall flanges, a plurality of movable bending meansdisposed in a line, each bending means having supports at spaced apartzones provided with rounded edges as the sole portions thereof on one Ormore of which rounded edges the plate is adapted to rest in unclampedcondition according to its length, a fixed bending means overhead withrespect to the movable bending means providing an abutment edge for eachof the latter as the sole plate-contacting portions of the movablebending means at said zones disaligned with respect to the coactingsupport and adapted to engage the upper surface of the plate, said fixedbending means having spaced parallel platecontacting edges intermediateand spaced from the supports, the movable bending means having aplate-contacting edge parallel to and intermediate the last mentionededges, means operable to move the foremost movable bending means towardthe fixed bending means to move the metal inwardly from the sides of theplate toward its longitudinal median line and then reversely move themetal through fulcruming and sliding of the plate on said parallel edgesof the coacting supports to bend the plate, said mechanism includingconnections to couple all movable bending means to operate in unitaryrelation, and control means to cause the movable bending means to ceaseoperation after predetermined movement so that there is clearance forspringback action of the plate at the center and both edge portions.

2. In apparatus for forming flat plate into angular configuration,bending means having spaced apart supports on edges of which the plateis adapted to rest in unclamped condition, bending means having edgesdisaligned with the first mentioned edges and outwardly thereof toengage the upper surface of the plate and having an abutmentintermediate said edges disaligned with the said supports provided withspaced edges parallel to said edges to engage the upper surface of theplate, edge means on the first mentioned bending means to engage thelower surface of the plate intermediate the edges of the abutment,mechanism operable to move one of said means relative to the other meansto move the metal inwardly from the sides of the plate toward itslongitudinal median line and then reversely move the metal throughfulcruming and sliding inwardly and outwardly with respect to thelongitudinal median line of the plate on said paralle1 edges of saidsupports to bend the plate.

3. In apparatus for forming flat plate into substantially trough-likeform having side wall flanges, means to initially bow the plate havingspaced parallel plate-contacting edges, edge means to support the platedurin said bowing so that the movement of metal thereof will be inwardlytoward the first-mentioned means, and means to thereupon line-contactthe metal in opposition to the first mentioned and second mentionedmeans intermediate the said parallel edges and also outwardly of theedge means to bend the metal with outward movement thereof, theconstruction enabling spring-back action at the center and side wallflanges of the form.

4. The method of forming cold metallic plate into an angularconfiguration while maintaining parallelism of the fibers of the metalconsisting in simultaneously moving the metal thereof inwardly withrespect to its side edges and bowing an intermediate portion of theplate, and in thereafter reversing the direction of movement of themetal to move the latter outwardly while reducing the bow of bowedintermediate portion and bending the portions of the plate along saidedges into side wall flanges, all parts of the plate during the inwardand reverse movements being free to slide.

5. The method of bending a flat metal plate in a machine having twobending means, one

of which has spaced elements, which methodconsists in disposing saidplate between the bends 7 ing means and resting it freely on saidelements, moving one of the bendin means relatively to the other to anextent short of trapping of the fibers of the plate with such otherbending means contacting the plate at spaced parallel lines and therebybending the plate and pulling the metal inwardly while leaving itopposite side portions free and fulcrumed on edges of said elements,resulting in a central relatively shallow portion and portions divergingtherefrom to the side edges of the metal, then bending the metal and itsside portions while forcing the metal outwardly on said edges by furtherrelative movement of the two bending means short of trapping of thefibers f the plate.

6. The method of bending a flat metal plate in a machine having twobending means, one of which has spaced elements, which method consistsin disposing said plate between the bending means and resting it freelyon said elements, hydraulically moving one of the bending meansrelatively to the other to a limited extent with such other bendingmeans contacting the plate at spaced parallel lines resulting in aconcave central portion and portions diverging therefrom, therebybending the plate and pulling the metal inwardly while leaving itsopposite side portions free and fulcrumed on edges of said elements, asanother stage in bending the terminals of said side portions in reversedirection into a plane approximately parallel to the plane of thecentral portion, and as a final stage in simultaneously flattening thecentral portion through contact at a line intermediate said parallellines on the opposite sides of the plate and said terminals.

'7. The method of bending a flat metal plate in a machine having twobending means, one of which has spaced elements, which method consistsin disposing said plate between the bending means and resting it freelyon said elements, moving one of the bending means relatively to theother to a limited extent and thereby bending th plate and pulling themetal inwardly while leaving its opposite side portions free andfulcrumed on edges of said elements, then bending the metal and its sideportions while forcing the metal outwardly on said edges by furtherrelative movement of the two bending means.

8. The method of bending a fiat metal plate in a machine having twobending means, one of which has spaced elements, which method consistsin disposing said plate between the bending means and resting it freelyon said elements, moving one of the bending means relatively to theother to a limited extent and thereby bending the metal and pulling themetal inwardly while leaving its opposite side portions free andfulcruined on edges of said element so as to have a shallow dishedcentral portion and'diverging portions extending therefrom, then bendingthe metal and its side portions while forcing the metal outwardly onsaid edges in thereverse direction angularlywith respect to theremainder of the diverging portions into a plane approximately parallelwith the central portion by further relative movement of the two bendingmeans through line contact with its convex surface approximately midwayof the ends of the dished portion.

9. An apparatus for forming fiat plate into substantially trough-likeform having sidewall flanges, bending means having spaced apart supportson which the plate is adapted to rest in unclamped position, bendingmeans in a zone between the zones of said supports having abut- .8 mentedges disaligned with respect to said sup-- ports to engage the uppersurface of the plate, mechanism operable to move one of said meansrelatively to the other means to pull the metal inwardly over edges ofthe supports from the sides of the plate toward the second bending meansthrough fulcruming and sliding of the plate on said edges to bend theplate.

10. An apparatus for forming flat plate into substantially trough-likeform having side wall flanges, bending means having supports at spacedapart zones provided with faces out of parallelism with the horizontalproviding edges at their summits as the sole portions thereof on whichthe plate may rest in unclamped position, bending means in a zonebetween the zones of said support having abutment edges disaligned withrespect to said support as the sole plate-contacting portions of thesecond-mentioned bending means to engage the upper surface of the plate,mechanism operable to move one of said means relative to the other meansto pull the metal inwardly from the sides of the plate toward thesecond-bending means and reversely push the metal through fulcruming andsliding of the plate on said edges of said supports to bend the platewhile enabling movement of the metal outwardly with final spring-backaction.

11. An apparatus for forming flat plate into substantially trough-likeform having side wall flanges, a plurality of movable bending means,each movable bending means having supports at spaced apart zonesprovided with edges as the summits thereof and the sole portions thereofon one or more of which the plate is adapted to rest in unclampedcondition according to its length, fixed bending means providing anabutment for each movable bending means disaligned with the respectivesupports thereof and adapted to engage the upper surface of the plate,said fixed bending means having an arched under-surface provided withspaced parallel plate-contacting edges intermediate and spaced from thesupports, the movable bending means having a platecontacting edge as itssummit parallel to and intermediate the respective last-mentioned edges,and mechanism operable to selectively move one movable bending means ora plurality of movable bending means toward the fixed bending means tomove the metal inwardly from the sides of the plate toward itslongitudinal median line and then reversely move the metal throughfulcruming and sliding of the plate on said parallel edges of saidsupport to bend the plate.

12. An apparatus for forming flat plate into substantially trough-likeform having side wall flanges, a plurality of movable bending means,each movable bending means having supports at spaced apart zonesprovided with edges as the summits thereof and sole portions thereof onone or more of which the plate is adapted to rest in unclamped conditionaccording to its length, fixed bending means providin an abutment foreach movable bending means disaligned with the respective supportsthereof and adapted to engage the upper surface of the plate, said fixedbending means having an arched undersurface provided with spacedparallel platecontacting edges intermediate and spaced from thesupports, the movable bending means having a plate-contacting edge asits summit parallel to and intermediate the respective last-mentionededges, and mechanism operable to selectively move one movablebendingmeans or a plurality of movable bending means toward the fixed bend-aing means to move the metal inwardly from the sides of the plate towardits longitudinal median line and then reversely move the metal throughfulcruming and sliding of the plate on said parallel edges of saidsupport to bend the plate, the bending means accordingly being of aconstruction which avoids compression of the fibers of the plate andpermits final spring-back action of the plate at the center and at boththe edge portions approximately simultaneously.

13.' An apparatus for forming fiat plate into substantially trough-likeform having side wall flanges, the apparatus being provided with a firstbending means having supports at spaced apart zones provided with edgesas the summits thereof and sole portions thereof on which the plate isadapted to rest in unclamped condition, a second bending means providingan abutment for the first bending means disaligned with the respectivesupports thereof and adapted to engage the upper surface of the plate,said second bending means having an arched under-surface provided withspaced parallel plate-contacting edges intermediate and spaced from thesupports, the first bending means having a plate-contacting edge as itssummit parallel to and. intermediate the last mentioned edges to engagethe lower surface of the plate, and mechanism operable to move one ofsaid bending means toward the other bending means to move the metalinwardly from the sides of the plate toward its longitudinal median lineand then reversely move the metal through fulcruming and sliding of theplate on said parallel edges of said supports to bend the plate.

14. An apparatus for forming flat plate into substantially trough-likeform having side wall flanges, the apparatus being provided with a firstbending means having supports at spaced apart zones provided with edgesas the summits thereof and sole portions thereof on which the plate isadapted to rest in unclamped condition, a second bending means providingan abutment for the first bending means disaligned with the respectivesupports thereof and adapted to en age the upper surface of the plate,said second bending means having an under-surface provided with spacedparallel plate-contacting edges intermediate and spaced from thesupports, the first bending means having a plate-contacting surfaceopposed to the last mentioned edges to engage the lower surface of theplate, and mechanism operable to move one of said bending means towardthe other bending means to move the metal inwardly from the sides of theplate toward its longitudinal median line and then reversely move themetal through fulcruming and sliding of the plate on said parallel edgesof said supports to bend the plate.

15. An apparatus for forming fiat plate into substantially trough-likeform having side wall flanges, the apparatus being provided with a firstbending means having supports at spaced apart zones provided with edgesat the summits thereof and sole portions thereof on which the plate iadapted to rest in unclamped condition, a second bending means providingan abutment for th first bending means disaligned with the respectivesupports thereof and adapted to engage the upper surface of the plate,said abutment being intermediate and spaced from the supports, the firstbending means having a platecontacting surface opposed to the abutmentand out of parallelism thereto to engage the lower surface of the plateshort of clamping thereof.

10 andmechanism operable to move one of said bending means toward theother bending means to move'the metal inwardly from the sides of theplate toward its longitudinal median line and then reversely move themetal through fulcruming and sliding of the plate on said parallel edgesof said supports to bend the plate.

16. The method of forming fiat metallic plate into substantiallytrough-like form having side wall flanges, comprising disposing andresting the plate in cold condition between opposed sections and on thelower sections of at least three spaced apart bending devices whereinthe plane offinal coaction of the sections of the intermediate bendingdevice is longitudinally disaligned with respect to the other bendingdevices, and in moving the sections on one side of the plate relativelyto the remainder of the sections at such areas, times and degree ofengagement of the said sections with the plate to bend the platewhileleavingall parts of the plate throughout an operation free to slideinwardly and outwardly with respect to the longitudinal median line ofthe plate, whereby trapping of the metal or distortion of its fiber isavoided.

17. The method of bending a cold metal plate consisting in cold drawingthe plate inwardly from an edge thereof to provide a flange adjacentsaid edge and a bowed portion inwardly spaced from said edge and out ofthe plane thereof by the action of bending means engaging the plate to adegree short of trapping of the fibers of the plate, and in thereafterreducing the degree of bow of said bowed portion while the plateisengaged by the bending means to a degree short of trapping of thefibers of the plate by reversely drawing the plate from the zone of saidbowed portion.

.18. The method of producing a flanged structure from a cold metal fiatplate, which comprises cold working the plate by subjecting it tobending action along spaced bending edges disposed approximately inparallelism and while engaging the plate to a degree short of trappingof the fibers of the metal, and moving the plate while so engaged inreverse directions with respect to opposite sides of and across saidedges.

19. A method of forming fiat plate into generally trough-like formconsisting in contacting the plate at spaced parallel lines and movingthe plate to bend it at said lines while loosely supported and unclampedfrom said lines to the marginal edges of said plate, resulting in acentral relatively shallow channel with sides diverging to said edges,and while the plate is still unclamped, in bending the terminals of thediver ing portions in the reverse direction into a plane approximatelyparallel to the plane of the central portion.

20. A method according to claim 19 in which the operation is effected instages the first consisting in contacting the plate at spaced parallellines and moving the plate to bend it at said lines while looselysupported and unclamped from said lines to the marginal edges of theplate and the second in bending the terminals of the diverging portionsin the reverse direction into a plane approximately parallel to theplane of the central portion.

21. A method of forming fiat plate into general- 1y trough-like formconsisting in disposing the fiat plate between two bending means andresting freely on spaced elements of one of such means, in moving one ofsaid means relatively to the other means to a limited extent to bend theplate with 11 its opposite side portions free and fulcrumed on edges. ofsaid elements, and in then bending the terminals of said portions onsaid edges through relative movement of the two bending means.

22. Apparatus for forming fiat plate into substantially trough-like formcomprising bending means having spaced apart supports on which the plateis adapted to rest in unclamped condition, bending means havinganabutment disaligned with said supports to engage the upper surface ofthe plate, mechanism operable to move one of said means relative to theother means to bend the plate through fulcruming and sliding on edges'of said supports.

EMMOR H. MILLARD. FREDERICK R. WILSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number UNITED STATES PATENTS Name Date Booth Apr, 4, 1854 Worthen et a1July 5, 1859 Henderson Dec. 22, 1896 Brown Dec. 17, 1901 Frey Feb. 5,1907 Klocke July 26, 1910 Minshull Nov. 29, 1910 Verdin et a1 Oct.3,1911 Small Aug. 9, 1921 Briggs et a1 Apr. 30, 1878 Ainsworth Mar. 25,1884 Barr Nov. 15, 1904 Bunker Jan. 8, 1929 Verson et a1 June 16, 1942.Klenzle June 27, 1939 Ogden et al Aug. 1, 1922

